Development of nanosensors and nanostructured materials from agricultural by-products for enhancement of food and agricultural productivity and for environmental sensing and remediation: Bench-scaling of the production of cellulosic nanocrystals from kawayang tinik (Bambusa blumeana) and their utilization for renewable nanomaterials

Date

2017

Abstract

Two general approaches to bench-scale the production of nanocellulose from Kawayang tinik (Bambusa blumeana J.A. and J.H. Schultes) were explored. The first approach retained acid hydrolysis with sulfuric acid as the final step to the production of cellulosic nanocrystals, but modified a number preparatory steps before Kraft pulping as well as the sequence of chemical treatment after pulping to determine the best combination that will give the highest yield while maintaining that cellulose in nano dimension is obtained as final product. Before pulping, changes employed were the use of hammermill to further physically disintegrate the cut bamboo culms for pulping, grinding of the bamboo chips using a Friction Grinder Supermass Colloider, and the use of steam explosion to soften the ligning before its removal via chemical reactions during pulping. There were no significant effects in achieving nanoscale sizes for the products via the pretreatment steps, but yield was considerably reduced with steam explosion because of material recovery issues involving minute sized particles. Consequently, only hammermilling was retained as a preparatory step prior to pulping. Pulping was also scaled up by using a 40-L pressure cooker with pressure and temperature gauges, which was heated using a LPG gas-fired stove that increased the rate at which the desired temperature was reached. After, pulping the best combination in terms of yield was produce d using a route that involves the following sequence: bleaching - digestion with sodium chlorite (preparation of holocellulose) - and digestion with 17.5% sodium hydroxide (preparation for alkali insoluble cellulose). Acid hydrolysis reaction was carried out using 46% sulfuric acid, at 45 deg C for 30 minutes. Post-hydrolysis treatments involved neutralization with NaOH, centrifugation, dialysis, and sonication. Portions of the samples were freeze-dried inpreparation for analyses using FTIR, SEM, AFM, and XRD but the rest of the nanocellu lose were kept in aqueous suspension to prevent aggregation. The second approach involved using the friction grinder supermass colloider (FGSC) for the mechanical fibrillation of the material, without a final acid hydrolysis step to produce nanocellulose. Instead, the bamboo pulp, in various stages of chemical treatment after pulping, were made to pass several times through the FGSC and the yield and properties (FTIR, SEM, AFM, XRD) determined by taking samples for arbitrarily determined number of passes. It was determined that nanosize fibrils were attainable by grinding up to 200 passes bamboo pulp, but the lignin tended to form an inseparable matrix that enveloped the fibrils. Increasing the number of passes to 400 (double) did not improve lignin removal. Mechanical fibrillation of the bleached pulp was tried next, and was also able to produce nanosize fibrils, but lignin remained as a nuisance. Next, digestion of the bleached pulp with sodium chlorite removed the lignin while retaining non-cellulosic carbohydrates (low molecular weight hemicelluloses), which when passed through the FGSC resulted in nanosize fibrils without lignin. With dimensions of 100 nm or less, this indicated that further chemical treatment was no longer necessary before grinding on the FGSC. Indeed, there were no significant differences in chemical and nanoscale properties between nanocellulose from holocellulose from nanocellulose derived from alkali-insoluble cellulose. Holocellulose preparation as the starting point for grinding with FGSC saves at least one chemical step prior to the production of nanocellulose. Application trials of the bamboo nanocellulose involved incorporating bamboo nanocellulose in thermoplastic starch, modified bamboo nanocellulose in low density polyethylene film (LDPE), and in fabricating nanopaper using nanocellulose, with and without termiticide. The latter was tested as physical barrier against subterranean termite, Coptotermes gestroi. Modification of the bamboo nanocellulose was done by chemical oxidation with 2,2,6,6,-tetramethylpiperidine-1-oxyl (TEMPO) followed by reaction in excess long chain alkyl amine (1-hexadecylamine) in the presence of N,N'–diisopropylcarbodiimide (DIC) and N-hydro xysuccinimide (NHS) in dimethyl sulfoxide (DMSO) with stirring for 24 hours at less than 30 deg C temperature following the procedure of Tan et al. (2015).

Language

English

Document Type

Article

Pages /Collation

100 leaves

En – AGROVOC descriptors

BAMBUSA; SPECIES; BAMBOOS; CELLULOSE PRODUCTS; CHEMICAL PULP; RENEWABLE RESOURCES; PULPING; PAPERMAKING

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